The invention concerns a method for controlling a wiper motor belonging to a wiper device for a motor vehicle windshield.
The invention also concerns a control unit implementing the inventive method and a wiper device for a motor vehicle windshield.
Almost all motor vehicles are equipped with wiping devices comprising at least one wiping element such as a wiper blade. The wiping element allows, via an alternating, rotational or linear sweeping movement, the wiping of a zone of the windshield of a vehicle powered by a continuous current electric motor powered by the battery via control of the driver, by an on-board computer or by other automation.
In a first state of the art, the detection of the ends of the sweeping course was not necessary because they depended on a transformation mechanism, generally of the crank connecting rod type which didn't need position information.
In a second state of the art, the need to control the course of the blade is apparent when one wants to place an electronic control unit between the driver's command or an automated command and the electric motor and today one knows how to detect the instantaneous position of the wiper blade or its docking on the wiping stops. In a certain measure, one also knows how to detect the instantaneous position of the blade in its course and, as a result of predetermined controls, controls the alternating movement by controlling the electric power supply of the electric wiping motor that produces the movement of the blade.
Unfortunately, numerous situations are encountered during use of the motor vehicle on which the wiper device is installed in which the control unit is no longer in a controlled state that corresponds to the real situation.
This is the case in performance or characteristic variations introduced by mechanical play or use, the placement of obstacles on the windshield or in the kinematical chain that transmits mechanical energy from the motor to the wiper blade, and still others, like the intentional displacement by a hand during its wiping path.
In another state of the art, one has proposed means to resolve certain problems occurring during real-life situations. Either it is necessary to re-standardize the system or the wiper device becomes unusable, which is unacceptable from a safety standpoint.
It would be desirable to remedy these inconveniences and to propose a standard wiping device that is simple to install, as well as an automatic initialization process of the command system.
With this goal in mind, the invention proposes a control method of a wiper motor equipped with a wiper device which powers at least one wiper blade moving on a windshield along an alternating path between two end-of-travel positions. The control process is characterized in that:
During a first initialization step,                to detect the first and second end-of-travel stops, such as those determined by construction of the associated device, then        to determine from these first and second end-of-travel stops, the first and second end-of-travel test zones and in each of the test zones the position of a software stop on which the blade changes its sweeping direction during normal operation;        during a normal operating step:                    to detect the position of the wiper blade relative to the first and second end-of-travel test zones, in order to determine the change of direction of the sweeping, and            to provide during at least one passage of the wiper blade in a test zone a variation of the position of the end-of-travel software stop, of the type that provides self-adaptation of the sweeping limits in time with mechanical use, play and other accidents.                        
According to another aspect of the invention, during the normal operating step, the situation of each end-of-travel test zone is calculated as a function of the detection of the docking of the physical end-of-travel stops.
According to another aspect of the invention, a first limit of each end-of-travel zone is determined based on the detection of the docking of an end-of-travel stop and by a second limit placed at a predetermined distance from the first limit.
According to another aspect of the invention, the variation of the position of each software stop is performed by incrementation of a positive and a negative pitch in such a way so that the software stop stays in its test zone.
According to another aspect of the invention, during normal operation, the control process also consists of detecting the presence of an obstacle on the alternating path of the wiper blade outside of the test zone, when it comes from an end-of-travel test zone, then to determine a wiper stop.
According to another aspect of the invention, during normal operation, the control process also comprises controlling a reverse return of the wiper blade from a predetermined distance, then a stop of a predetermined duration, and finally a return towards the position of the obstacle, at least a predetermined number of times.
According to another aspect of the invention, during normal operation, the control process also controls, from the detection stop position of an obstacle returning behind the wiper blade towards the end-of-travel test zone where the blade began.
According to another aspect of the invention, during normal operation, the control process also consists of controlling next an initialization step, so that the obstacle placed in the path of the wiper blade is considered a physical end-of-travel stop and allows a sweeping step of normal functioning according to graded amplitude.
According to another aspect of the invention, during normal operation, the control process also consists of detecting the presence of an obstacle in an end-of-travel zone, then to produce a stop sweeping command, then a return in the opposite sweeping direction.
According to another aspect of the invention, the control process also consists of incrementing an obstacle detection counter in an end-of-travel test zone, then to detect when the counter reaches a predetermined value, then to re-execute a new initialization step.
The invention also concerns a wiper control unit in order to put in place the control process defined above. The wiper control unit comprises:                means for determining an end-of-travel test zone at a first sweeping end the input of which is connected to a means of detecting the docking of the wiper blade on a physical end-of-travel stop;        means for determining an end-of-travel test zone at a second sweeping end the input of which is connected to a means of detecting the docking of the wiper blade on a physical end-of-travel stop;        means for determining the position of an end-of-travel stop in each end-of-travel zone; and        means for controlling the movement of a wiper motor;so that the sweeping direction is reversed during each docking of a software end-of-travel stop and so that the position of each software end-of-travel stop is varied, at the end of determined sweeping, in order for the software end-of-travel stop to stay inside the test zone.        
According to another aspect of the invention, the control unit also comprises means for detecting the presence of an obstacle outside of an end-of-travel test zone, the output signal of which is transmitted to the activation input of a generator that comprises, separately or together; means of controlling the reverse return of the wiper blade from a predetermined distance, a means of controlling the reverse return of the wiper blade up to the preceding software end-of-travel stop, means producing a stop time of a predetermined duration, then a return towards the detected position of the obstacle, a counter of the detected number of obstacles from an intermediate stop position producing an active output signal when the detected number surpasses a predetermined value, so that the control means of a reverse return of the wiper blade up to the preceding software end-of-travel stop is activated, the counter thus being reset, a counter of the number of detected of a obstacle in an end-of-travel test zone, producing an active output signal when the detected number surpasses a predetermined value, so that at least one of the means for determining an end-of-travel test zone and one software end-of-travel stop are activated by taking the position of the obstacle as the end-of-travel stop.
According to another aspect of the invention, the control unit also comprises means for detecting the presence of an obstacle in the end-of-travel test zone, the output signal of which is transmitted to the activation input of a generator that controls a reverse return towards the opposite end-of-travel test zone.
According to another aspect of the invention, the control unit also comprises a means for counting the number of sweeps, during the course of which an obstacle was encountered, then when a predetermined number of sweeps has been reached, for recalculating the situation of the end-of-travel test zone in which an obstacle was detected.
The invention also concerns a wiper device incorporating a wiper control unit defined above. The wiper device comprises a wiper motor powered under the control of a control device in order to detect a start/stop command from a user or an on-board computer, connected to the said wiper control unit, which also receive signals representative of the right and left physical ends-of-travel such that the relative position and the detection of the obstacle generated by a detection means relative to the output shaft of the wiper motor, mechanically connected to a reductor and to a rotational movement conversion device of the redactor output shaft in sweeping movement applied to at least one wiper blade.